Circuit breaker with vent opening



Allg- 17, 1965 J. H. LEONARD 3,201,550

CIRCUIT BREAKER WITH VENT OPENING Filed April 5, 1964 United States Patent O l 3,201,550 CIRCUIT BREAKER WITH VENT OPENING James H. Leonard, `Cedar' Rapids, Iowa, assigner to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 3, 1964, Ser. No. 357,049 7 Claims. (Cl. 200-144) The instant application relates to circuit breaker mechanisms housed within narrow casings and is a continuation-in-part of copending application Serial No. 11,768 tiled February 29, 1960.

In recent years it has been the practice to construct circuit breakers for home and light industrial applications with casings whose widths are one inch or multiples thereof. More recently, the trend has been to supply individual circuit breaker protection to many circuits, even those carrying light loads. Because of this the capacity of existing panelboards, while sufiicient electrically, were not sufiicient in physical size to accommodate the greater numbers of circuit breakers. Further, panelboards having the requisite physical size to accommodate the greater number of circuit breakers were wasteful of material and space.

Thus, it became necessary to construct circuit breakers having narrow housings. For example, a typical circuit breaker of amp rating was usually provided with a molded casing having a one inch width. A circuit breaker of this rating can be replaced by a circuit breaker whose molded insulating housing is one-half inch in width.

Cost is maintained at a minimum without sacrificing reliability of operation by eliminating as many elements as possible and also providing a construction wherein many elements perform dual functions.

The circuit breaker of the instant invention includes novel means for deionizing and directing arcing gases through the case vent opening. This means is comprised of a narrow elongated slit at the bottom of the case formed by the cooperation of the mating halves comprising the case. The slit forming portions of the mating halves are offset so that the slit is not formed as a small opening in the center of a large surface but as an opening positioned adjacent to a wall. The wall initially acts to create a turbulence in the arcing gases and thereafter serves to direct the deionized gases through the vent opening.

In addition the oifsets at one end thereof define a curved boundary for the arc chamber. This results in better tunneling of arcing gases to the vent opening thereby improving arc extinction.

Accordingly, it is a primary object of the instant invention to provide a narrow molded case circuit breaker which is economical to construct, is reliable in operation and is simple to calibrate.

Another, object is to provide improved venting for the arc gases by utilizing a housing construction wherein an optimum degree of turbulence is created and at the same time the gases are directed out of the circuit breaker case so as to prevent excess back pressures from being created. g These as well as other objectsv of the instant invention shall become readily apparent after reading the following description of the accompanying drawing in which:

FIGURE l is a side elevation of a circuit breaker constructed in accordance with the instant invention with 3,201,550 Patented Aug. 1'7, 1965 the cover of the casing removed to reveal the operating mechanism.

. FIGURE 2 is a fragmentary cross-section of the breaker housing taken through line 2-,-2 of FIGURE 1 looking in the direction of arrows 2-2.

FIGURE 3 is a cross-section similar to FIGURE 2 showing a modified form of the instant invention.

Now referring to the iigures. Circuit breaker 20 includes a housing comprised of a case 21 and cover 22 mated to each other along line 23 and secured by rivets 23a. For a detailed description of the operating mechanism construction and operation reference is made to the aforesaid copending application Ser. No. 11,768.

The current path through circuit breaker 20 comprises line terminal 24, conducting strap 25, stationary contact 26, movable contact 27, contact arm 28, the pressure joint 29 at the upper arm of contact 28, releasable cradle 30, bimetal 31, conducting braid 32 and load terminal contact member 33.

Spring 79 acts as a gripping means for a load conductor (not shown) which passes through case opening '78 into engagement with load contact 33. Adapter means 77, of a type fully described in U.S. Patent,3,095,524 issued June 25, 1963 to J. H. Leonard et al., entitled Panelboard Adapter, and assigned to the assignee of the instant invention, is utilized to electrically connect line terminal 24 to a panelboard bus bar (not shown).

kCircuit breaker 20 includes an operating member 34 having an extension 35 projecting upwardly through an opening 36 in the top of housing 21, 22 to provide a manual operating handle. Operating member 34 is also provided with an arcuate portion 37 extending in the direction of movement of handle 35 and disposed within arcuate groove 38 of case 21 and a similar groove in cover 22. The upper end of handle arm 39 extends into suitable recesses of operating member 34 while the lower end of arm 39 abuts against a rounded internal formation of case 21 to form a pivot 40 for operating member 34.

Main operating spring 41 is secured at one end thereof 42 to arm 39 Where the bifurcated upper end thereof engages member 34 While the other end 43 of spring 41 is connected to movable contact arm 2S. Spring 41 is a tension spring comprised of an open loop with elongated arms extending in opposite directions. The tension force exerted by spring 41 urges the upper end of contact arm 2S to abut cradle 30 at joint 29.

Sub-assembly (cradle 30, bimetal 31, intermediate latch 48, etc.) is pivoted on post 45 extending through aperture 44 near the apex of V-shaped cradle 30. With subassembly 100 in the latched position and circuit breakver 20 closed as in FIGURES 1 and handle 35 is moved to the right with respect to FIGURE l, at such time as the spring end at 42 passes to the right of a line joining spring end 43 and joint 29, the line of action of spring 41 will be so positioned so as to affect a snap opening of contacts 26, 27 by pivoting contact arm 28 in a counterclockwise direction about joint 29 to the Off position.

The reverse action takes place as handle 35 is moved to the left back to its position of FIGURE 1. During the latter operation, at such time as the line of action of spring 41 extending between spring ends 42, 43 passes to the left of the line joining spring end 43 and joint 29, contact arm 23 will be snapped in a clockwise direction about joint 29 to the closed or On position of FIGURE 1.

Since contact arm 23 abuts cradle 36 at joint 29 to rv; the right of embossment 45, the force exerted by main operating spring 41 acts to rotate sub-assembly 100 counterclockwise about pivot 45. However, sub-assembly 100 is restrained against movement in a counterclockwise direction through the engagement of intermediate v `latch member 48 with main latch member 51.

Main latch member 51 is constructed of spring material and includes a portion of reduced area which extends over to back of magnet 52 so as to form a pivot at 53 for armature 54 which is secured toV main latch member 51 by rivet 55. i

Magnet 52 is of generally U-shaped cross-section with braid 32 passing between the arms of the U to form the energizing turn therefor. The biasing action of the spring material forming main latch member 51 urges armature 54 in a clockwise direction about its pivot 53 away from magnet 52. The lower end of armature 54 abuts a case formation 56 to establish the air gap between armature 54 and magnet 52 and also establishes the latching position for member 51. Magnetic tripping takes place when a predetermined magnitude of current flows through braid 32 causing magnet 52 to generate flux which attracts armature 54 counterclockwise about pivot 53. This moves main latch member 51 counterclockwise with .respect to FIGURE 1 so that sub-assembly 100 is no longer restrained. Thus, sub-assembly 1010 under the iniiuence of main operating spring 41 rotates in a counterclockwise direction about pivot 45. When pivot 29 moves to the left of the line of action of spring 41 in its posi- Ation of FIGURE 1, spring 41 will urge contact arm 28 in a counterclockwise direction about pivot 29 to bring about a snap opening of contacts 26, 27.

With circuit breaker tripped `sub-assembly 100 is positioned by the abutment of handle arm extension 60 and cradle surface 61 while offset 75 of contact arm 28 abuts cover formation '716.

Magnetic tripping resetting is accomplished by moving operating handle to the extreme right position from its intermediate tripped position. During this movement handle arm extension 60 engages cradle 30 along surface 61 so that sub-assembly 11i@ is moved clockwise against the force of spring 41 to the latched position. As latch member 48 moves past latch member 51V the rounded portion 63 of intermediate latch member 48 cams latch 51 to the right until latch surface 64 passes below the lower end of main latch member 51.

Time delay tripping is accomplished by a deflection lofthe free end of bimetal 31 out of the plane of movement of cradle 36. When `this deflection Vis sufficient to free bimetal offset 31a from intermediatelatch 48 the action of tension spring 41 will rotate cradle 30 in a counterclockwise direction about pivot 45. Initially intermediate latch member 48 is retained by main latch member 51 so that there is relative movement between cradle 39 and intermediate latch member 48` about pivot 49. As the distance between pivot 49 and main latch member 51 increases, a point is reached where intermediate latch member 48 is free of main latch member 51 and the sub-assembly 100 moves counterclockwise to the tripped position.

Resetting after thermal tripping is accomplished by moving handle 35 from its intermediate trip to the extreme right. At the latter portion of this movement intermediate latch member 48 engages case embos'smenti' lwhich forces intermediate latch member 48 in a counterclockwise direction about its pivot 49 to a point where member 4S is free of the edge of bimetal extension 31a and at this time the free end of bimetal 31 moves toward the plane of movement of cradle 30 into latching position.

Cover 22 is mated with case 21 to form housing chamber 80 wherein the operating mechanism is disposed, and also forms vent opening 81 (FIGURE 2) which extends for distance X (FIGURE 1) along the bottom of housing 21, v22. Vent 81 is greatly elongated being very narrow in width, say .020. It is to be noted that the cover i? surface 82 forming vent 81 extends inwardly beyond the case surface 33 forming vent 81. Sloping surface 84 adjacent the inner edge of vent surface 83 serves to direct arcing gases toward surface 82.

Thus, gases formed during circuit interruption in rushing toward vent 81 initially experience turbulence within chamber since vent 81 is so narrow. After the gases are substantially deionized the upper portion of surface 82 not confronted by surface 83 acts to direct the deionized gases through vent 81 out of housing 21, 22.

It is noted that the inner boundaries 82a, 83a, of surfaces 82, 83, respectively, form a Curved boundary for arc chute 99 through which contact 27 moves. It has been found that this curved shape results in reduced burning and gas generation with better funnelingof arcing gases through vent opening 81.

Further improvement may be achieved by rounding one or both of the interior edges 82a', 83a of surfaces 82' 83- defining vent 81 of FIGURE 3. f

Thus, I .have provided a novel circuit breaker mechanism which is especially adapted for narrow housings. In particular, vent opening 81 and the surfaces 82, 83 defining opening 81 facilitate arc extinction.

Although I have here described a preferred embodi- -ment of my novel invention, many variations and modifications will now be apparent to those skilled in the art, and I therefore prefer to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A circuit breaker comprising:

cooperating contact means;

operating means;

a housing, said housing comprising first and second housing Amembers mounted in abutting relationship toform a chamber wherein said cooperating contact means and operating means are disposed,

each of said housing members being box-like in struc- .ture and comprising a substantially flat surface and a first, second, third, and fourth wall surrounding and extending from said flat surface, the first wall of said first housing member extending for a major portion thereof a lesser distance from said fiat surface than said second, third, and fourth walls, confronting faces of said first walls of said housing mem- -bers forming an elongated yvent opening, said confronting faces` of said first walls being defined by a length which corresponds to the length of 'said major portion and a width which corresponds to the thickness of said first walls, the face of said first wall of said second housing member having a greater width than the face of said first wall of said first housing member, the dierence in width of said confronting faces serving to direct arcing gases from said chamber through said vent opening.

2. A circuit breaker as set forth in claim 1 in which there is an arc chamber at one end of said opening; said arc chamber being partially defined by a curved intersection of said surfaces first wall and an adjacent wall of each said housing members.

3. A circuit breaker as set forth in claim 2 in which the interior surface defining the distance said first wall of saidfirst housing member extends from said fiat surface is a sloping surface.

4. A circuit breaker as set forth in claim 1 in which at least one face of said confronting faces of said housing members is provided with a rounded interior edge.

5. A circuit breaker Vas set forth in claim 1 in which said operating means includes an operating member having a portion extending through an opening inthe top of said housing, and said vent opening residing in thebottom of said housing.

6. A circuit breaker as set forth in claim 5 in which 5 the interior surface dening the distance said first wall of said rst housing member extends from said fiat surface is a sloping surface.

'7. A circuit breaker as set forth in claim 5 in which there is an arc chamber at the bottom of said housing 5 References Cited by the Examiner UNITED STATES PATENTS 2,020,334 11/35 Sachs 200-116 2,627,563 2/53 Thomas 20G-144 ROBERT K. SCHAEFER, Acting Primary Exmnner. 

1. A CIRCUIT BREAKER COMPRISING: COOPERATING CONTACT MEANS; OPERATING MEANS; A HOUSING, SAID HOUSING COMPRISING FIRST AND SECOND HOUSING MEMBERS MOUNTED IN ABUTTING RELATIONSHIP TO FORM A CHAMBER WHEREIN SAID COOPERATING CONTACT MEANS AND OPERATING MEANS ARE DISPOSED, EACH OF SAID HOUSING MEMBERS BEING BOX-LIKE IN STRUCTURE AND COMPRISING A SUBSTANTIALLY FLAT SURFACE AND A FIRST, SECOND, THIRD AND FOURTH WALL SURROUNDING AND EXTENDING FROM SAID FLAT SURFACE, THE FIRST WALL OF SAID FIRST HOUSING MEMBER EXTENDING FOR A MAJOR PORTION THEREOF A LESSER DISTANCE FROM SAID FLAT SURFACE THAN SAID SECOND, THIRD, AND FOURTH WALLS, CONFRONTING FACES OF SAID FIRST WALLS OF SAID HOUSING MEMBERS FORMING AN ELONGATED VENT OPENING, SAID CONFRONTING FACES OF SAID FIRST WALLS BEING DEFINED BY A LENGTH WIDTH CORRESPONDS TO THE LENGTH OF SAID MAJOR PORTION AND A WIDTH WHICH CORRESPONDS TO THE THICKNESS OF SAID FIRST WALLS, THE FACE OF SAID FIRST WALL OF SAID SECOND HOUSING MEMBER HAVING A GREATER WIDTH THAN THE FACE OF SAID FIRST WALL OF SAID FIRST HOLUSING MEMBER, THE DIFFERENCE IN WIDTH OF SAID CONFRONTING FACES SERVING TO DIRECT ARCING GASES FROM SAID CHAMBER THROUGH SAID VENT OPENING. 